Modern data storage devices are used in a multitude of computer environments to store large amounts of data in a form that is readily available to a user. Generally, a disc drive is a data storage device having one or more data storage discs forming a disc stack that is rotated by a motor at high speeds. Each disc has a data storage surface divided into a series of generally concentric data tracks where data is stored, such as in the form of magnetic flux transitions.
A data transfer member, such as a magnetic transducer, is moved by an actuator to selected positions adjacent the data storage surface to sense the magnetic flux transitions in reading data from the disc, and to transmit electrical signals to induce the magnetic flux transitions in writing data to the disc. The active elements of the data transfer member are supported by suspension structures extending from the actuator. The active elements are maintained a small distance away from the data storage surface as the data transfer member flies upon a fluid bearing generated by a fluid flow caused by the spinning discs. In some cases the fluid can be air, or alternatively it can be other fluids such as an inert gas like helium.
A continuing trend in the industry is toward ever-increasing the data storage capacity and processing speed while maintaining and even reducing the physical size of the disc drive. Consequently, continual efforts are being made to miniaturize the data transfer member and supporting structures, increase data storage densities, and decrease data transfer member fly height, resulting in overall increased sensitivities to vibration and noise. At the same time, continual increases in disc speed for faster data access time have resulted in the fluid flow becoming a more significant impact to be considered.
A number of measures can be taken to minimize the effects of the outwardly spiraling fluid flow on the components. Shrouding the discs, for example, reduces the amount of mixing of flow currents from opposite sides of a disc at the disc edge. Otherwise, these opposing currents can impart coupling forces on the disc at the edge causing disc flutter. Strippers are also used to divert the fluid flow away from the data transfer member.
In any event, the fluid flowing outwardly in the disc stack sets up pressure gradients resulting in turbulence when high and low pressure flows mix. For this reason it is advantageous to configure the shroud and otherwise provide fluid strippers or dams to establish a flow circuit guiding the flow away from the disc stack back and then into the disc stack. In doing so, a smooth transition is necessary in order to prevent turbulent flows or excessive back pressures.
It is also advantageous to place a porous filter in the path of this recirculation flow circuit in order to trap fluid borne particulates. Use of a filter can be problematic, however, because the resulting decreased flow rate and the increased back pressure can propagate perturbations upstream to adversely affect the rotating disc.
One attempted solution to this problem has been to isolate the filter as far as possible from the disc. Somewhat elaborate channels have been employed to lengthen distance between the disc and the filter. This solution is limited, however, due to space constraints. As the filter is moved farther away within a fixed space it must necessarily be made smaller. The reduced size of the filter and the convoluted recirculation circuits limit the flow rate capability of the recirculation circuit.
Contrarily, it is advantageous to maximize the size of the filter. Increasing the filter face area reduces the pressure drop across the filter and makes higher flow rates possible without effecting adverse back pressures. It has been determined that a maximum size filter can be achieved by using a curved filter as a guiding vane in the recirculation circuit to guide the fluid flow while filtering it. It is to these improvements and others as exemplified by the description and appended claims that embodiments of the present invention are directed.